From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794419402; b=42S3Irq9hFlNk2YhI+uXKRkXz6qvEU2FxuAd6D634Hvk/WSW/80IQ8XyrUzClElGOK7/ N6et5KsekP/ex+Bike8pBVZK9kdOR94w9OxN75jGWV13NOWLJt5J19ANWkL7yC+HjIhtO zrFcgSJxFItUo7tkz6QQVdZvfB36sz/12U5v0K1TJrHCmrO2RGGm8l5F4g1NjgNjcOABO H1gWUn2X/CnjvSC1ynaUNsoXISKV9fV2V4ldmNfvlFWvMacoeQ5Ukbr4ty88zprekwA6i Nk2ornFTibgwW4OOHFZP9ctVA/bbIQKHovBScYijf6TTpdyEiOLZB3ol2Omf7m6+ppw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794419402; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=dGSSrsltGu3YoArYKQxdKd439Q9tXLkVKgzBuJFs6os=; b=N7EpFTMTI+i0WDWosVX/Qku4fv3OGcRCiiu3zeYLTQDO3qamGJ7wuxyjCHs0mxGqfyyH nKaau4NnXsQ1Ap/SJri4nVERKSEfX11Rp0GSPyxoc2snOVJAIF8gjk0kF/Pq8pLh62EFt jv04sKPHxuG6V7W/Y9jIrcHQ3sTlXBHw+yfkMfSRBg66JlknCKVR0Z1oHTNKV6XkDb2Cd uAnn9RTtzeu+I+ZoW9Q3v/q2jUeXcxpUefSeteVhF4SBwjSxXpdDh2oRR9zAOevvEYYtT 1rReu3l4w6lI6hWEjkurcwsef5NFq+yx0LIckmqc6HztcRGUk/++ZkXEmQvC54qerRQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b="TMxIZ/gq"; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C0635606A31C for ; Wed, 11 Nov 2026 17:50:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=TMxIZ/gq Received: by smtp.kernel.org (Postfix) with ESMTPSA id F1F501F00A05; Wed, 11 Nov 2026 17:50:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794419402; bh=dGSSrsltGu3YoArYKQxdKd439Q9tXLkVKgzBuJFs6os=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=TMxIZ/gqUA1zwk1DXVIdoEZsCDCmK+JVbLc7FqGsbceo8GOK1vrY/j7tD4UT2l4OS vM/IQn9RASPJxsVsKi2TloB+eGRS8TSPR8SM+D5KxeO/7QWYSq7Nbs8CzWD0KxIcS1 F5z37UdjjrukHjBGNWfFcHGcsRZUmih8DB9bi6+nTNdOZ4ocZgfCZjjdKiMgZNMuxm VlT2l7iHwAoYY608SzBt8BAp3rMdeowQVSz4+nNjvH5cqNg9ZIcS8DImnU7pTFK7T/ jmURVs9WYBaTfG/5Fe8r4jO2a9IYVQ9ZOJ6gdH7hvCPRVxC6s/n7hanRRjFtuh7+sU A2eWS9/he5mXQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Samarth Narang , Andrew Morton , Lance Yang , "David Hildenbrand (Arm)" , Xu Xin , Chengming Zhou , Peter Xu , Kiryl Shutsemau , Mike Rapoport , Sasha Levin Subject: [PATCH 5.15.y] mm/ksm: keep soft-dirty when merging a page Date: Wed, 11 Nov 2026 12:49:59 -0500 Message-ID: <20261111174942.3699316-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261109202210-failed-5.15-2efc6332f18b@kernel.org> References: <20261109202210-failed-5.15-2efc6332f18b@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Samarth Narang [ Upstream commit 2efc6332f18bfd848f74f3d5ba45b31450601faa ] replace_page() maps the KSM page with a PTE built from scratch, so the soft-dirty bit of the PTE it replaces is lost. A page written since "clear_refs 4" then no longer shows as soft-dirty once it is merged, and a soft-dirty based dumper treats it as unchanged. Copy the soft-dirty bit from the original PTE to the new PTE. Link: https://lore.kernel.org/20261021182157.1873726-1-samarth.colleges@gmail.com Fixes: 0f8975ec4db2 ("mm: soft-dirty bits for user memory changes tracking") Signed-off-by: Samarth Narang Signed-off-by: Andrew Morton Reviewed-by: Lance Yang Acked-by: David Hildenbrand (Arm) Assisted-by: LLM Cc: Xu Xin Cc: Chengming Zhou Cc: Peter Xu Cc: Kiryl Shutsemau Cc: Mike Rapoport Cc: [ sashal: adjusted context because flush_cache_page() uses *ptep instead of ptep_get(ptep) ] Signed-off-by: Sasha Levin --- mm/ksm.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/mm/ksm.c b/mm/ksm.c index 3ed1bd6085f91..26d9beca82095 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -1163,6 +1163,10 @@ static int replace_page(struct vm_area_struct *vma, struct page *page, dec_mm_counter(mm, MM_ANONPAGES); } + /* Preserve soft-dirty when replacing the page. */ + if (pte_soft_dirty(orig_pte)) + newpte = pte_mksoft_dirty(newpte); + flush_cache_page(vma, addr, pte_pfn(*ptep)); /* * No need to notify as we are replacing a read only page with another -- 2.53.0